In the case of a large number of domestic appliances or domestic machines, it is necessary to heat up a fluid medium, such as for example water, and that can be effected by means of one or more heating systems. In that case, a medium circuit can be provided, a pump arranged in the circuit causing circulation of the medium in the circuit.
Basic aspects for such a heating system are that, like all other components of the medium circuit, the system is to take up only a small amount of space and is to be inexpensive to produce. Furthermore the heating system is to be simple to assemble. In addition reliable safeguarding of the heating system must be guaranteed upon the occurrence of a critical operating condition which can result in plastic components within the domestic appliance melting or catching fire. In the case of some domestic appliances moreover it may be necessary to prevent the medium to be heated from basically exceeding a predetermined temperature, for example in the case of a dishwashing machine the boiling temperature of the washing water.
For instance, international application WO 92/05675 discloses a heating system in which an elongate heat transfer plate of copper is in heat-conducting contact at its one end with a tubular heater which projects into a tub of a laundry washing machine. The other end of the heat transfer plate is passed through a fixing flange to the outside of the tub. That end is divided into two portions of which one is in contact with an actuating device for a heat-sensitive control, whereas the other portion is connected to a thermal protection device.